In British Pat. No. 1,409,768, there are described several heterocyclic derivatives of guanidine in which the heterocyclic moiety is a 5- or 6-membered saturated 1,3-diazacarbocyclic-2-ylidene. These derivatives are unsubstituted on the imino nitrogen of the guanidine moiety. In contrast, the compounds of the present invention differ by being a saturated mono-aza heterocyclic derivative of guanidine, and, furthermore, they carry a bulky substituent on the imino nitrogen of the guanidine moiety. Additional prior art, but further related, may be represented by German Offen. No. 2,321,330 which corresponds to U.S. Pat. No. 3,993,469 and German Offen. No. 2,502,397 which corresponds to U.S. Pat. No. 3,903,084.